Set sampling controls instruction

ABSTRACT

A measurement sampling facility takes snapshots of the central processing unit (CPU) on which it is executing at specified sampling intervals to collect data relating to tasks executing on the CPU. The collected data is stored in a buffer, and at selected times, an interrupt is provided to remove data from the buffer to enable reuse thereof. The interrupt is not taken after each sample, but in sufficient time to remove the data and minimize data loss.

This application is a continuation of U.S. Ser. No. 12/244,300, entitled“Central Processing Unit Measurement Facility,” filed Oct. 2, 2008,which is hereby incorporated herein by reference in its entirety.

BACKGROUND

This invention relates, in general, to facilitating processing within aprocessing environment, and in particular, to efficiently collectingdata relating to execution of tasks within the processing environment toenhance processing thereof.

Improved system performance and reduced errors are high priority goalsof many processing environments. In an effort to achieve these goals,diagnostic and tuning tools are employed. One such tool is a samplingfacility that gathers data relating to processing that occurs within aprocessing environment.

Specifically, a sampling facility is used to periodically take asnapshot of a central processing unit executing within the environmentand to record state information associated with the central processingunit. This information is used for debugging and/or to improve systemperformance.

Today, at each sampling time, the data is collected, stored in aregister, and an interrupt is provided to the control program. Uponinterruption, the control program reads out the sample data, resets theregister and resumes the operation. This interruption at each samplinginterval creates significant system overhead, and in some real-timeenvironments, may even distort the measured data. This overhead problemcauses users to limit the amount of sample data to be collected, andthus, limit the practical use of the sampling facility.

BRIEF SUMMARY

Based on the foregoing, a need exists for an enhanced sampling facilitythat is less disruptive and more effective than current samplingfacilities. In particular, a need exists for a sampling facility thatdoes not interrupt the control program at each sampling interval. A needexists for a sampling facility that is able to better manage interrupts,such that they occur less often.

The shortcomings of the prior art are overcome and additional advantagesare provided through the provision of a computer program product toexecute a machine instruction in a central processing unit. The computerprogram product comprises a storage medium readable by a processingcircuit and storing instructions for execution by a computer forperforming a method. The method includes, for instance, obtaining amachine instruction for execution, the machine instruction being definedfor computer execution according to a computer architecture, the machineinstruction including, for instance, an opcode field identifying a setsampling controls instruction; and a first field identifying a generalregister, the contents of which are added to the contents of a secondfield to form a second operand address; and executing the machineinstruction, the executing including placing in one or more controlregisters one or more sampling controls of a request block located inone or more storage locations designated by the second operand address.

Methods and systems relating to one or more aspects of the presentinvention are also described and claimed herein. Further, servicesrelating to one or more aspects of the present invention are alsodescribed and may be claimed herein.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

One or more aspects of the present invention are particularly pointedout and distinctly claimed as examples in the claims at the conclusionof the specification. The foregoing and other objects, features, andadvantages of the invention are apparent from the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1 depicts one embodiment of a processing environment to incorporateand use one or more aspects of the present invention;

FIG. 2A depicts one example of various sampling control registers usedin accordance with an aspect of the present invention;

FIG. 2B depicts one example of the contents of a table entry addressregister of FIG. 2A, in accordance with an aspect of the presentinvention;

FIG. 2C depicts one example of the contents of a data entry addressregister of FIG. 2A, in accordance with an aspect of the presentinvention;

FIG. 3 depicts one embodiment of the structure of a sampling buffer usedin accordance with an aspect of the present invention;

FIG. 4A depicts one embodiment of the fields of a basic sampling dataentry, in accordance with an aspect of the present invention;

FIG. 4B depicts one embodiment of the fields of a diagnostic samplingdata entry, in accordance with an aspect of the present invention;

FIG. 4C depicts one embodiment of the fields of a trailer entry, inaccordance with an aspect of the present invention;

FIGS. 5A-5B depict one embodiment of the logic associated with updatinga sampling buffer, in accordance with an aspect of the presentinvention;

FIG. 5C depicts one embodiment of the logic associated with providing aninterrupt to read the collected data from the buffer, in accordance withan aspect of the present invention;

FIG. 6 depicts one embodiment of an overview of the logic associatedwith performing a sampling function, in accordance with an aspect of thepresent invention;

FIG. 7A depicts one embodiment of the logic associated with processingperformed asynchronous to execution of the sampling facility to enablethe storing of identifiers with the collected data, in accordance withan aspect of the present invention;

FIG. 7B depicts one example of a format of a Set Program Parametersinstruction used in accordance with an aspect of the present invention;

FIG. 8A depicts one embodiment of a format of a Query SamplingInformation instruction used in accordance with an aspect of the presentinvention;

FIG. 8B depicts one embodiment of the fields associated with aninformation block associated with the Query Sampling Informationinstruction, in accordance with an aspect of the present invention;

FIG. 9A depicts one embodiment of a format of a Set Sampling Controlsinstruction used in accordance with an aspect of the present invention;

FIG. 9B depicts one embodiment of a request block associated with theSet Sampling Controls instruction, in accordance with an aspect of thepresent invention;

FIGS. 10A-10B depict one embodiment of the logic to deploy samplinglogic on one or more processing units, in accordance with an aspect ofthe present invention; and

FIG. 11 depicts one embodiment of a computer program productincorporating one or more aspects of the present invention.

DETAILED DESCRIPTION

In accordance with an aspect of the present invention, a CPU measurementsampling facility is provided that takes a snapshot of the centralprocessing unit on which it is executing at specified sampling intervalsto collect data regarding tasks (e.g., applications, modules, functions,instructions, etc.) executing on the central processing unit. This datais collected for statistical estimation of performance characteristics.The collected data is stored in a buffer and at selected times, aninterrupt is provided to empty the buffer to enable reuse thereof. Theinterrupt is not taken after each sample, but in sufficient time toremove data from the buffer and minimize data loss.

One embodiment of a processing environment incorporating and using oneor more aspects of the present invention is described with reference toFIG. 1. Processing environment 100 is, for instance, a multiprocessingenvironment including a plurality of processors 102 (e.g., centralprocessing units (CPUs)), a memory 104 (e.g., main memory) and one ormore input/output (I/O) devices 106 coupled to one another via, forexample, one or more buses 108 or other connections.

As one example, each processor 102 is a z10 processor based on thez/Architecture® of International Business Machines Corporation, Armonk,N.Y., and one or more of the processors execute a control program, suchas the z/OS® or z/VM® operating systems offered by InternationalBusiness Machines Corporation. One example of the z/Architecture® isdescribed in “z/Architecture—Principles of Operation,” SA22-7832-06,Seventh Edition, February 2008, which is hereby incorporated herein byreference in its entirety. z/OS®, z/Architecture®, and z/VM® areregistered trademarks of International Business Machines Corporation,Armonk, N.Y., U.S.A. Other names used herein may be registeredtrademarks, trademarks or product names of International BusinessMachines Corporation or other companies.

To provide information to facilitate processing within the processingenvironment, data is gathered on a regular basis. This data is used, forinstance, for debugging purposes and/or to improve system performance.For example, a CPU measurement sampling function 110 is executed on oneor more of the CPUs and for each CPU on which it is executing, itprovides a snapshot of the logical CPU at each specified samplinginterval, which is a processing time interval as seen by the CPU. Eachsnapshot produces a set of sample data, which includes, for instance,the instruction address of an instruction being executed and some stateinformation about the CPU. This sample data is stored, for instance, inone or more sample data blocks of a buffer.

In one example, the CPU measurement sampling facility includes twosampling functions, several sampling control registers, several externalinterruption events and various instructions, each of which is describedbelow.

The two sampling functions include, for instance, basic sampling anddiagnostic sampling. The basic sampling function provides a set ofarchitected sample data. The sample data includes an instructionaddress, the primary address space number (PASN), and some stateinformation about the CPU, as examples. This allows tooling programs tomap instruction addresses into modules or tasks, and facilitatesdetermination of hot spots. The diagnostic sampling function provides aset of non-architected sample data, and is intended for use by hardwaredesign analysts, operating systems, sophisticated compilers, andinternal subsystems. Since the sample data provided by the diagnosticsampling function may reveal detailed internal hardware design, aconsole with a controlled password may be used to authorize use of thefunction.

Both the basic sampling and diagnostic sampling functions use the samesampling control registers, the same sampling buffer structure, the sameexternal interruption events, and the same instructions. The maindifference between these two functions is the sample data.

The sample data size and format for each sampling function are modeldependent and are determined by, for instance, a 16-bit data entryformat code, which is stored in each sample data. The sample dataprovided by the basic sampling function is not included in the sampledata provided by the diagnostic sampling function. To get meaningfuldiagnostic sampling data, both sampling functions should be activated.The state of each sampling function can be individually set by executinga Set Sampling Controls instruction, which is described below. Bothsampling functions are disabled by initial CPU reset, clear reset orpower-on reset.

In one example, the external interruption events include an invalidentry address alert, an incorrect sample data block table entry alert, aprogram request alert, a sampling authorization change alert, and a lossof sample data alert. These events are part of an external interruptionsubclass, called the measurement alert subclass. The subclass mask bit,e.g., bit 58 of control register zero, is provided. This bit isinitialized to one, which enables the interruption.

The CPU measurement sampling facility provides a number of samplingcontrol registers. Except for authorization controls, the contents ofthese control registers are cleared to zeros by initial CPU reset, clearreset or power-on reset; and may also be cleared to zeros by executingthe Set Sampling Control instruction that disables all samplingfunctions. Authorization controls are set or reset by an external means.

Examples of sampling control registers are described with reference toFIG. 2A. In one example, these registers are hardware registers withinthe CPU. As shown, sampling control registers 200 include, for instance,a table entry address register (TEAR) 202; a data entry address register(DEAR) 204; a maximum buffer size indicator 206; a sampling functionstate control register 208; a sampling interval register 210; and a hostindicator 212, each of which is described below.

As shown in FIG. 2B, table entry address register 202 is, for instance,64 bits, and includes, an address of a current sample data block tableentry 220. It is unpredictable whether the address is real or absolute.

Referring to FIG. 2C, data entry address register 204 is, for instance,64 bits, and includes an address of the next sample data block dataentry 230. Again, it is unpredictable whether the address is real orabsolute.

In one example, maximum buffer size indicator 206 is one bit. When theindicator is zero, the maximum size of the sample data block tables andthe size of the sample data blocks are 4K bytes. When the indicator isone, the maximum size of the sample data block tables and the size ofthe sample data blocks are 1M bytes.

Sampling function state control register 208 is, for instance, 6 bits,and three bits are assigned to the basic sampling function and the otherthree bits are assigned to the diagnostic sampling function. For eachsampling function, there are, for instance, three state controlindicators, including: authorization control (A), enable control (E),and activation control (C).

Sampling interval register 210 is, for instance, 64 bits, and thecontents of the register specify the number of CPU cycles within eachsampling interval.

Host indicator 212 is, for instance, one bit and is available to CPUs atthe logical partition level (described below). When the CPU is runningat the logical partition level and if a sampling function is active, thehost indicator when zero specifies that the contents of the programparameter register are stored into the guest program parameter field ofthe sample data blocks by the sample data block update process; the hostindicator, when one, specifies that the contents of the programparameter register are stored into the host program parameter field.

When the CPU is in the operating state, a sampling function can be inany of the following four states, as examples: unauthorized, disabled,inactive, and active.

Unauthorized: When a sampling function is in the unauthorized state, thefunction cannot be used and no sample data is stored. An external meansis provided to authorize or unauthorize the use of the function.

Disabled: When a sampling function is in the disabled state, thefunction is authorized for use, but the control program has not enabledthe function yet. In this state, no new sample data is stored, and thecontents of the sample data blocks remain unchanged, and no samplingcontrol, except for authorization controls, is preserved.

Inactive: When a sampling function is in the inactive state, thefunction is authorized, enabled, and deactivated. In this state, no newsample data is stored, the contents of the sample data blocks remainunchanged, and sampling controls are preserved and can be extracted.

Active: When a sampling function is in the active state, the function isauthorized, enabled, and activated. In this state, new sampling data isstored during each sampling interval and sampling controls can beextracted.

When the CPU enters the stopped state from the operating state, activesampling functions are stopped. When the CPU enters the operating statefrom the stopped state, sampling functions resume the states they werein when they were last stopped.

The following table summarizes actions that cause state transitions of asampling function:

To From Unauthorized Disabled Inactive Active Unauthorized —* Externalcontrol Not applicable Not applicable Disabled External control —*Enabled & Enabled & deactivated by activated by SSCTL. SSCTL. InactiveExternal control Disabled by —* Activated by SSCTL, or by SSCTL. reset¹.Active External control Disabled by Deactivated by —* SSCTL, or SSCTL orby reset¹. errors². Explanation: ¹Each enabled sampling function isdisabled by initial CPU reset, clear reset or power-on reset. ²Eachactive sampling function is deactivated by an invalid entry addressalert, an incorrect sample data block table entry alert, or a loss ofsample data alert. *When a sampling function is in the unauthorized,disabled, inactive, or active state, if execution of SSCTL sets thestate controls to the same state as the original state, the statecontrols are considered successfully set. — No action required. SSCTLThe SET SAMPLING CONTROLS instruction. Not applicable This statetransition cannot occur.

The sample data is stored in a buffer in, for instance, main memory. Forexample, a number of sample data blocks (that comprise a buffer) areallocated by the control program for the machine to store sample dataduring each sampling interval. Each sample data block is designated by ablock link entry in a sample data block table. The current entry of thesample data block table is designated by the contents of the table entryaddress register and the next data entry of the sample data block isdesignated by the contents of the data entry address register. Oneexample of the structure of a sampling buffer, in accordance with anaspect of the present invention, is depicted in FIG. 3.

Referring to FIG. 3, a sampling buffer 300 includes one or more sampledata block tables (SDBTs) 302 and one or more sample data blocks (SDB)304. In this particular example, three (3) sample data block tables areshown, which are coupled in a circular linked list. Further, in thisexample, there are a plurality of sample data blocks. It is understoodthat other examples of the sampling buffer can have more, less or thesame number of SDBTs and/or more, less or the same number of SDBs, asshown in this particular example.

The contents of a table entry address register (TEAR) 306 point to thecurrent entry of a sample data block table 302. There are two kinds ofentries in each sample data block table including, for instance: blocklink entries 308 and table link entries 310. Each block link entry 308includes a sample data block (SDB) origin, and each table link entryincludes a sample data block table (SDBT) origin. In this particularembodiment, each sample data block table starts at an integral boundaryof 16 bytes, and each entry is 8 bytes. Each sample data block table 302includes a number of block link entries 308 and one table link entry310. A specified bit in each entry (e.g., bit 63) distinguishes a blocklink entry from a table link entry. When bit 63 is zero, the entry is ablock link entry; when bit 63 is one, the entry is a table link entry. Atable link entry is the last entry in the sample data block table. Theactual size of a sample data block table is determined by the locationof the table link entry, and does not exceed the size specified in themaximum buffer size indicator. The origin and the table link entry of asample data block table cannot be separated by an integral boundary ofthe maximum buffer size, in this embodiment.

When a maximum buffer size indicator 320 is zero, a specified portion(e.g., bits 0-51) of a block link entry include the origin of a sampledata block in real or absolute store. When the sample data block originis to be placed in the data entry address register, it is appended withzeros (e.g., 12 zeros) on the right to form a 64 bit address and theaddress is then placed in the register.

When maximum buffer size indicator 320 is one, specified bits (bits0-43) of a block link entry include the origin of a sample data block inreal or absolute storage. When the sample data block origin is to beplaced in the data entry address register, it is appended with a numberof zeros (e.g., 20) on the right to form a 64 bit address and theaddress is then placed in the register.

In one example, bits 0-59 of table link entry 310 include the origin ofa sample data block table in real or absolute storage. When the sampledata block table origin is to be placed in the table entry addressregister, it is appended with a number of zeros (e.g., 4) on the rightto form a 64 bit address and the address is then placed in the register.

Continuing to refer to FIG. 3, the contents of a data entry addressregister 330 designates the next data entry 332 of a sample data block304. Each sample data block starts at an integral boundary of themaximum buffer size. The size of a sample data block is equal to thesize specified in the maximum buffer size indicator.

In one example, there are two kinds of entries in each sample datablock, including, for instance, data entry 332 and a trailer entry 336.The last number of bytes (e.g., 64) of a sample data block form thetrailer entry; all other space in the block is used to form dataentries.

When at least one sampling function is active, a data entry is storedduring each sampling interval. If only the basic sampling function isactive, the data entry stored is a basic sampling data entry; if onlythe diagnostic sampling function is active, the data entry stored is adiagnostic sampling data entry. If both sampling functions are active,the data entry stored is a combined data entry. Each of these dataentries is explained in further detail below.

One example of the basic sampling data entry is described with referenceto FIG. 4A. In one example, a basic sampling data entry 400 includes,for instance, the following fields:

-   -   Data Entry Format Code 402: Bits 0-15 of the data entry include        the format code of the data entry.    -   Number of Unique Instructions (U) 404: Bits 20-23 of the data        entry specify the number of unique, completed instructions that        were executed simultaneously during the sampling cycle when the        unique cycle indicator is on.    -   A pipelined CPU can execute multiple instructions concurrently        in an overlapped fashion: each of these instructions being        executed concurrently is in a different pipeline stage.        Furthermore, on some models, each stage of a pipelined CPU may        execute multiple instructions simultaneously.    -   During an instruction execution, a unique cycle indicator is        turned on for one cycle at the sample point, that is the place        in the CPU the sample data is taken from. The sampling point        depends on the model, but is the same for all instructions        executed on the same model. For a pipelined CPU, the sampling        point is usually a particular pipeline stage. Depending on the        model, it is unpredictable when the unique cycle indicator is        turned on during an instruction execution. This field includes        the number of instructions executed simultaneously at the        sampling point when the unique cycle indicator is on.    -   When a sampling time occurs and if the sampling point is not        busy because either the CPU is in the wait state or because of        delay in some other pipeline stage, the contents of this field        are set to zero.    -   The contents of this field can be used to estimate cycles per        instruction when a sufficiently small sampling interval and an        adequately larger number of samples are used.    -   The cycles per instruction for a particular measurement can be        estimated by dividing the number of busy samples, that is        samples with the wait state bit (described below) being set to        zero, by the total number of unique instructions in all busy        samples.    -   DAT Mode (T) 406: Bit 26 of the data entry includes the data        address translation (DAT) mode bit in the Program Status Word        (PSW) of the CPU.    -   Wait State (W) 408: Bit 27 of the data entry includes the wait        state bit in the PSW of the CPU.    -   Problem State (P) 410: Bit 28 of the data entry includes the        problem state bit in the PSW of the CPU.    -   Address Space Control (AS) 412: Bits 29-30 of the data entry        include the address space control in the PSW of the CPU.    -   Invalid Indication (I) 414: Bit 31 of the data entry indicates        whether the entry is valid or invalid. When the bit is zero, the        entry is valid; when the bit is one, the entry is invalid. An        entry is set to invalid when sample data in the entry are not        consistent.    -   Primary ASN 416: Byte offsets 6-7 of the data entry include the        Primary Address Space Number (PASN) in bits 48-63 of control        register 4 of the CPU.    -   Instruction Address 418: Byte offsets 8-15 of the data entry        include the instruction address of an instruction that the CPU        was executing during the sampling cycle.    -   Instruction addresses are treated as real addresses in the real        mode; as primary virtual addresses in the primary address mode,        secondary space mode, or access register mode; and as home        virtual addresses in the home space mode.    -   When the sampling point is executing multiple instructions        simultaneously during the sampling cycle, only the address of        one instruction among these simultaneously executed instructions        is reported. The selection of which instruction address to be        reported is model dependent.    -   On some models, the address of the target instruction of Execute        is not reported in the same data. When the wait state bit is        one, the contents of this field are unpredictable. When a        sampling time occurs and if the sampling point is not executing        any instruction because of delay in some other pipeline stage,        it is unpredictable which address of the instructions being        executed concurrently in the CPU is reported.    -   Guest Program Parameter 420: Byte offsets 16-23 of the data        entry include the current program parameter register if the CPU        is not running at the logical partition level or if it is        running at the logical partition level and the host indicator is        zero. If the CPU is running at the logical partition level and        the host indicator is one, zero is stored in this field.    -   Host Program Parameter 422: Byte offsets 24-31 of the data entry        include the current program parameter register if the CPU is        running at the logical partition level and the host indicator is        one. Otherwise, the contents of this field are unpredictable.

One example of a diagnostic sampling data entry 440 is described withreference to FIG. 4B. In one example, diagnostic sampling data entry 440includes:

-   -   A data entry format code 442: Bits 0-15 of the data entry        includes the format code of the data entry.    -   Maximum buffer size 444: Bit 19 is intended to indicate the        maximum buffer size. Zero indicates 4K bytes, and one indicates        1 megabytes.    -   Invalid Indication (I) 446: Bit 31 of the data entry indicates        whether the entry is valid or invalid. When the bit is zero, the        entry is valid; when the bit is one, the entry is invalid. An        entry is set to invalid when sample data in the entry are not        consistent.    -   The rest of this entry includes non-architected sample data.

When both the basic sampling function and the diagnostic samplingfunction are active, the sample data stored during each samplinginterval is a combined data entry, which includes a basic sampling dataentry followed by a diagnostic sample data entry.

When a combined data entry is to be stored, it is completely stored inthe current sample data block if there exists enough space. When thereis not enough space in the current sample data block, if there is enoughspace in the next sample data block, then the entire combined sampledata is stored in the next sample data block. The basic sampling dataentry and the diagnostic sampling data entry of a combined data entryare not stored in different sample data blocks, in this example. Whenthe combined sample data is discarded because of no space available, thesample overflow count of the current sample data block is incremented byone.

One embodiment of the fields associated with a trailer entry aredescribed with reference to FIG. 4C. Each trailer entry is, forinstance, 64 bytes and resides in the last 64 bytes of a sample datablock. In one example, a trailer entry 450 includes, for instance:

-   -   Block Full Indicator (F) 452: Bit zero of byte offset 0 of the        trailer entry is a block full indicator. When the indicator is        one, the sample data block is full.    -   Alert request control (A) 454: Bit 1 of byte offset 0 of the        trailer entry is the alert request indicator. When the indicator        is one and the sample data block becomes full, a program request        alert external interruption event is recognized at the        completion of the sample data block update process. Herein, the        sample data block is considered full when its block full        indicator is set, regardless of whether it is entirely full. If        the block has additional space, but not enough to store the next        sample, the indicator is set and the block is considered full.    -   The setting of the alert request control is selectable. For        example, it can be set in every x (e.g., 10) data blocks. Thus,        even if one data block of the buffer is full, there need not be        an interrupt until a data block is reached with the indicator        set, such as after the tenth full data block. The selection of        10 is only one example; any other desired number may be used.        Thus, an interrupt may not be taken after the sample interval or        even if one data block is full.    -   Sample overflow count 456: Bytes offsets 8-15 of the trailer        entry include the number of sample data entries that have been        lost because the sample data block is full.    -   Timestamp 458: Byte offsets 16-31 of the trailer entry include        the time-of-day (TOD) clock value at the time when the sample        data block becomes full.

When a program request alert occurs, it is expected that the program(e.g., control program, such as an operating system) reads out sampledata from the sample data blocks that are full. To free up these blocks,the program shall reset the block full indicator (F) and the sampleoverflow count, and shall also reestablish an alert request control (A).Updating these fields in a sample data block shall be performed, in oneexample, as an interlocked update using, a Compare Double and Swapinstruction. All of these reads and updates are performed while samplingfunctions remain active.

When the CPU is in the operating state and at least one samplingfunction is active, the sample data block update process is performed ateach sampling time. The process locates space for the new data entry,forms the entry, and updates the contents of the data entry addressregister so that the register contents designate the location of thenext data entry.

During the sample data block update process, if any address is formedthrough the addition of a value to another address, a carry out of bitposition zero of the address, if any, is ignored. Similarly, when thecontents of the sample overflow count field is incremented, a carry outof bit position zero of the count, if any, is ignored.

Accesses to a sample data block are not subject to key controlledprotection; nor are they subject to low address protection.

When storage access to a sample data block entry or sample data blocktable entry is performed, if the address is invalid, a measurement alertexternal interruption event (invalid entry address) is recognized, andactive sampling functions for that CPU are placed in the inactive state.An entry address is invalid if, for instance, the address is in therange 0-8191; if the designated sample data block entry is inside thetrailer entry; or if the designated storage location is not available inthe configuration.

When storage access to a sample data block table entry is performed, ifany incorrect SDB table entry is detected, a measurement alert externalinterruption event (incorrect sample data block table entry) isrecognized, and active sampling functions for that CPU are placed in theinactive state. A sample data block table entry is incorrect if theentry is a table link entry and it designates another table link entry,or if the last table entry is not a table link entry.

The contents of the data entry address register are used to locate thenext data entry in the current sample data block. If the next data entryresides inside the trailer entry (e.g., last 64 bytes) of the sampledata block, then a measurement alert external interruption event(invalid entry address alert) is recognized and sampling functions areplaced in the inactive state.

One embodiment of the logic associated with updating a sampling buffer,in accordance with an aspect of the present invention, is described withreference to FIGS. 5A-5B. Referring to FIG. 5A, initially, sample datahas been obtained during a sampling function and it is to be stored inthe buffer, STEP 500. A determination is made as to whether the blockfull indicator in the trailer entry of the current sample data block isset (e.g., equal to one), INQUIRY 502. If the block full indicator isset, then at this point, it indicates that there is insufficient spacein the buffer to store the data. The contents of the sample overflowcount field of the trailer entry are incremented by one, STEP 504, andthe sample data to be stored is discarded, STEP 506. This completes theupdate process, STEP 508.

Returning to INQUIRY 502, if, however, the block full indicator in thetrailer entry of the current sample data block is zero, a determinationis made as to whether there is enough space to store the sample data,INQUIRY 510. If the block full indicator is zero and there exists enoughspace, then the sample data is stored in the next data entry, STEP 512,and the contents of the data entry address register are incremented bythe data entry size, STEP 514. The update process is complete, STEP 508.

On the other hand, returning to INQUIRY 510, if the block full indicatoris not set and there is not enough space to store the sample data in thenext data entry, then the block full indicator in the trailer entry ofthe current sample data block is set to one, STEP 520 (FIG. 5B), and thetime of day clock value is placed in the timestamp field of the trailerentry, STEP 522.

Thereafter, a determination is made as to whether the alert requestindicator in the trailer entry is one, INQUIRY 524. If the alert requestindicator in the trailer entry is one, a measurement alert externalinterruption event (program requested alert) is recognized at the end ofthe update process, STEP 526. Thereafter, or if the alert requestindicator is not set, the contents of the table entry address registerare incremented by the SDB table entry size so that the next entry inthe SDB table becomes the current SDB table entry, STEP 528. The currentSDB table entry is fetched and bit 63 of the entry is examined, STEP530. If bit 63 of the SDB table entry is zero, the entry is a block linkentry and includes a sample data block (SDB) origin; if bit 63 is one,the entry is a table link entry and includes a sample data block table(SDBT) origin.

If the fetched entry is the last entry in the SDB table, (i.e., theentry is the last entry before reaching the maximum buffer size),INQUIRY 532, and if the entry is not a table link entry (i.e., bit 63 ofthe entry is zero), INQUIRY 534, then a measurement alert externalinterruption event (incorrect SDB table entry alert) is recognized, STEP536. Active sampling functions are placed in the inactive state and theupdate process is complete, STEP 538.

Returning to INQUIRY 534, if it is the last entry and bit 63 is one,then the address of the origin of the SDB table specified in the entryis placed in the table entry address register so that the specifiedtable becomes the current SDB table, STEP 540. The current SDB tableentry is fetched and bit 63 of the entry is examined, STEP 542. If bit63 is one, INQUIRY 544, indicating that the SBD table entry pointed toby the table link entry is itself a table link entry, a measurementalert external interruption event (incorrect SDB table entry alert) isrecognized, STEP 536. Active sampling functions are placed in theinactive state and the update process is complete, STEP 538.

However, if bit 63 is zero, INQUIRY 544, then the address of the originof the sample data block specified in the entry is placed in the dataentry address register so that the block becomes the current sample datablock, STEP 546. Processing then continues at INQUIRY 502 (FIG. 5A), asdescribed above.

Returning to INQUIRY 532 (FIG. 5B), if the fetched entry is not the lastentry in the SDB table (i.e., not the last entry before reaching theboundary), and if bit 63 of the fetched table entry is zero, INQUIRY550, then processing continues at STEP 546, as described herein.However, if bit 63 of the fetched entry is one, indicating there are nomore entries in the table, even though the table has more space, thenprocessing continues with STEP 540, as described herein.

As indicated with reference to STEP 526, in response to determining thatan alert request is set in the trailer entry of a sample data block thatis indicated as full, a measurement alert external interruption event isrecognized at the end of the update process. One embodiment of thisprocessing is described with reference to FIG. 5C.

Referring to FIG. 5C, an interruption is recognized at the end of theupdate process, STEP 580. In response thereto, the control program readsthe data stored in one or more sample data blocks (e.g., the blocks thatare full, or all the blocks that have data or a subset thereof) andwrites that data to DASD or another storage medium, STEP 582.Additionally, in an interlocked update operation, the control programresets the block full indicator in the trailer entry of any of theblocks that were full, STEP 584, and re-establishes an alert requestcontrol STEP 586. In one example, the re-establishing includes setting(or leaving set) the same alert indicator that initiated the interrupt.In other examples, however, one or more other alert indicators can beset. An alert indicator can be set in one or more trailer entries,depending on how frequently the data is to be dumped.

The alert indicator is set, for instance, in at least one data block,which is selected to provide sufficient time to dump the data before thebuffer is full, minimizing the loss of sample data. If, however, a smallamount of data is lost, the collected data still continues to be useful.On the other hand, if a significant amount of data is lost, which isimplementation dependent, then the collected sample data is ignored.

The buffer update process described with reference to FIGS. 5A-5C ispart of an overall sampling process that takes place to capture sampledata. The sampling process begins by an operator request, in response towhich a sampling function is initiated. There may be one or moresampling functions initiated by one or more operators concurrently. Oneembodiment of an overview of a sampling process is described withreference to FIG. 6.

Referring to FIG. 6, initially, an operator invokes a sampling functionand specifies various parameters including, for instance, the samplingfrequency, F, (e.g., the number of samples to be collected per minute),the duration of the sampling run in minutes, D, and the type of sampling(e.g., basic, diagnostic, or combined), STEP 600.

Additionally, the control program issues a Query Sampling Information(QSI) instruction, described below, that provides information about thesampling facility, STEP 604. In one example, this information includesthe basic sampling data entry size (BSDES) in bytes, the diagnosticsampling data entry size (DSDES) in bytes, and the CPU speed=Ccycles/microseconds. With the obtained information, the control programcalculates the sampling interval for each processor in the measurement=icycles/sec, STEP 606. For instance,

F=overall sampling frequency in samples/minute;

p=number of processors involved in the measurement;

f=(F/60)/p=individual sampling frequency for each processor insamples/second;

C=CPU speed in cycles/(10**-6) seconds;

i=(1/f)C=individual sampling interval for each processor incycles/sample.

Further, the individual sampling frequency (defined above), f, thesample data entry size, L, and the specified duration of the samplingrun, D, are used to calculate how large the data buffer for eachprocessor needs to be, STEP 608. The sample data entry size, L, iscalculated using the specified sampling type and the size of each entrytype (BSDES and DSDES) returned by the QSI instruction. For instance,

L=sampling data entry size in bytes;

-   -   if only basic sampling is used, L=BSDES;    -   if only diagnostic sampling is used, L=DSDES;    -   if both basic and diagnostic sampling are used, L=BDES+DSDES;

f=individual sampling frequency for each processor in samples/second;

D=intended duration of the run in minutes;

B=f*L*D*60=buffer size in bytes needed for all of the samples on anindividual processor for the entire sampling run.

Based on the above information, the control program allocates storagefor the buffer, STEP 610. In accordance with an aspect of the presentinvention, the total buffer size need not be allocated. Instead, only aportion of the buffer is allocated and at specific times, an interruptis initiated to remove data from the buffer and that same buffer may bereused. Storage is allocated for the desired buffer size and the storageis formulated into the form of the sampling data buffer described withreference to FIG. 3.

The buffer size allocated by the control program is to be large enoughso that the control program can service the interruption before theallocated buffer is full. Allocating a buffer larger than this minimumvalue will require the control program to be interrupted lessfrequently. The time needed between control program interruptions is toguarantee servicing of each interrupt before the next is presented. Thecontrol program considers these factors when determining the portion ofthe needed buffer size to allocate, STEP 610.

The minimum size of the buffer to be allocated for each processorinvolved in the measurement, b, is calculated using the individualsampling frequency, f, the sample size, L, and the control programservice interval, T. For instance,

T=time in sec between control program interrupts needed to service thebuffer;

b=f*L*T=minimum allocated buffer size in bytes.

Once the minimum and maximum values have been calculated, the controlprogram determines a practical buffer size, including a safety margin.For example, the minimum buffer size, b, is multiplied by a value of 4to allow the asynchronous writing of the buffer to occur without losingsamples being collected concurrent to the write operation; it isunderstood that the write operation takes a nontrivial amount of time tocomplete.

Thereafter, the control program issues a Set Sampling Controlsinstruction, described below, to activate the sampling function, STEP612. In response to issuing this instruction, sampling is performed andthe sampled data is handled in the manner described above with referenceto FIGS. 5A-5C.

Asynchronous to the above, in accordance with an aspect of the presentinvention, a dispatcher of the control program issues a Set ProgramParameter instruction 700 (FIG. 7A), each time the dispatcher dispatchesa task. The Set Program Parameter instruction tags the task with anidentifier identifying the specific task. This identifier is providedalong with the sample data (e.g., identifier is retrieved from aregister and included with data) such that it is known for which taskthe data belongs. Since the dispatcher is performance critical, there isno test to determine if the measurement facility is activated. Instead,this instruction is issued each time the dispatcher dispatches a task.In one example, if the configuration is not configured for sampling,then the instruction is executed as a no operation.

One embodiment of the Set Program Parameter instruction is describedwith reference to FIG. 7B. As one example, a Set Program Parameterinstruction 750 includes the following fields:

-   -   Op code 752: This field includes the operation code that        specifies the Set Program Parameter instruction;    -   B₂ 754 and D₂ 756: The contents of the general register        designated by the B₂ field are added to the contents of the D₂        field to form a second operand address.

In execution, the eight byte program parameter in storage locationsdesignated by the second operand address is placed in a programparameter register. In one example, this register is a 64-bit register,and the contents of this register are cleared to zeros by initial CPUreset, clear reset or power-on reset. As one particular example, theprogram parameter register is included within a state descriptionmaintained in real storage.

The Query Sampling Information instruction, referred to above, is usedto place information about the CPU measurement sampling facility in aninformation block designated by the second operand address of theinstruction. In one example, a Query Sampling Information instruction800 (FIG. 8A) includes, for instance:

-   -   Op code 802: This field includes the operation code that        specifies the Query Sampling Information instruction;    -   B₂ 804 and D₂ 806: The contents of the general register        designated by the B₂ field are added to the contents of the D₂        field to form a second operand address.

In one example, the information block 820 (FIG. 8B) is 64 bytes andincludes the following:

-   -   Sampling State Controls 822: Byte offsets 0-3 of the information        block include the state controls for the basic sampling and        diagnostic sampling functions and have the following format, in        one example:

-   -   Basic Sampling Data Entry Size (BSDES) 824: Byte offsets 4-5 of        the information block include an unsigned binary integer,        specifying the size in bytes of the basic sampling data entry.        This information is hard-coded, in one example, in the machine.    -   Diagnostic Sampling Data Entry Size (DSDES) 826: Byte offsets        6-7 include an unsigned binary integer, specifying the size in        bytes of the diagnostic sampling data entry. This integer is        hard-coded, in one example, in the machine.    -   Minimum Sampling Interval 828: Byte offsets 8-15 of the        information block include the minimum sampling interval in        number of CPU cycles. This information is hard-coded, in one        example, in the machine.    -   Maximum Sampling Interval 830: Byte offsets 16-23 include the        maximum sampling interval in number of CPU cycles. This        information is hard-coded, in one example, in the machine.    -   TEAR Contents 832: When the basic sampling or diagnostic        sampling function, or both, are enabled, byte offsets 24-31 of        the information block include the contents of the table entry        address register. When neither the basic sampling nor diagnostic        sampling function is enabled, zeros are stored in byte offsets        24-31 of the information block.    -   DEAR Contents 834: When the basic sampling or diagnostic        sampling function, or both are enabled, byte offsets 32-39 of        the information block include the contents of the data entry        address register. When neither the basic sampling nor the        diagnostic sampling function is enabled, zeros are stored in        byte offsets 32-39 of the information block.    -   CPU Speed 836: Byte offsets 44-47 include an unsigned binary        integer, which specifies the CPU speed in number of CPU cycles        per microsecond. This information is provided by the machine.

The Set Sampling Controls instruction, an example of which is describedwith reference to FIG. 9A, is used to update the sampling controls. Inone embodiment, a Set Sampling Controls instruction 900 includes thefollowing format, in one example:

-   -   Op Code 902: This field includes the operation code that        specifies the Set Sampling Controls instruction;    -   B₂ 904 and D₂ 906: The contents of the general register        designated by the B₂ field are added to the contents of the D₂        field to form a second operand address.

During instruction execution, the sampling controls in the request blockin storage locations designated by the second operand address are placedin the corresponding sampling control registers. The values of thecontrols in the request block are provided by the operator and/or thecontrol program, as indicated below.

In one example, the request block is 64 bytes and includes the followingfields, as described with reference to FIG. 9B:

-   -   S 922: Bit 0, S, of the request block specifies the maximum        buffer size indicator, as specified by the operator.    -   H 924: When the CPU is running at the logical partition level,        bit 1, H, of the request block is the host indicator. When the        CPU is not running at the logical partition level, bit 1 is        ignored and treated as zero. This is specified by the control        program.    -   E_(s) 926: Bit 54, E_(s), of the request block specifies the        basic sampling enable control, which is set based on an input        parameter from the operator;    -   E_(d) 928: Bit 55, E_(d), of the request block specifies the        diagnostic sampling enable control, which is set based on an        input parameter from the operator.    -   C_(s) 930: Bit 62, C_(s), of the request block specifies the        basic sampling activation control, which is set based on an        input parameter from the operator.    -   C_(d) 932: Bit 63, C_(d), of the requested block specifies the        diagnostic sampling activation control, which is set based on an        input parameter from the operator. Bits 2-53 (925) and 56-61        (929) of the request block are zeros.

The specified enable and activation controls of sampling functions areset only if both sampling functions can make a valid state transition.If a sampling function cannot make a valid state transition, thespecified state controls are not set for any sampling function.

When a sampling function is set to the active state from the disabled,inactive, or active state, the additional controls, including themaximum buffer size indicator, the host indicator, sampling interval934, table entry address register contents 936, and the data entryaddress register contents 938 are placed in the sampling controlregisters. When no sampling function is placed in the active state bythe operation, the additional controls are ignored and are not placed inthe sampling control registers.

When a sampling function is to be set to the active state from thedisabled, inactive, or active state, and if the requested samplinginterval is outside the supported range, no sampling control, includingany state control, in the sampling control registers is changed and aspecification exception is recognized. The supported sampling intervalrange is between the maximum and minimum sampling intervals,inclusively, provided by executing the Query Sampling Informationinstruction.

In one example, when the enable and activation controls for bothsampling functions are set, condition code 0 is set. When the enable andactivation controls are not set, condition code 3 is set.

Described in detail above is a CPU measurement facility, whichperiodically takes a snapshot of the central processing unit on which itis executing, and records the CPU state information, including theinstructions being executed (e.g., Op codes, whether there is a problemwith an instruction, etc.) At each sampling time, the sample data isplaced in a buffer. When the buffer has a defined amount of data, aninterrupt is presented in order to remove data from the buffer.

In accordance with an aspect of the present invention, a samplemechanism is provided to collect sample data from the machine withoutfrequent intervention from the operating system. The operating systemallocates sample data blocks in real storage for the machine to storesample data. When the amount of sample data to be collected is extremelylarge, an aspect of the present invention allows the operating system toallocate storage for only a fraction of the total sample data. An alertmechanism is provided to allow the operating system to mark a blockrequesting that the machine generate an alert interruption when thissample will not fit in this sample data block. This allows the operatingsystem to read out sample data blocks that have been filled up by themachine and to release them for machine use. Also, there is a fullindication associated with each sample data block. This is used by themachine to tell the operating system that the block has been filled (oralmost filled) by the machine. In addition, there is an overflow countassociated with each sample data block. This is used to keep track ofthe number of sample data entries lost because the sample data blocksare full. This provides a hint to the operating system, when overflowoccurs, whether the measured data can still be used or the samplingfunction must be re-executed. Furthermore, to facilitate the operatingsystem to figure out the sampling interval and the amount of storage forsample data blocks, information about the maximum sampling interval,minimum sampling interval, and CPU speed is provided by a queryinstruction.

In yet a further aspect of the present invention, a technique isprovided for deploying one or more aspects of the sampling logic on oneor more processing units. One embodiment of the deployment logic isdescribed with reference to FIGS. 10A-10B.

Referring to FIG. 10A, initially, a determination is made as to whetherthere are any programs that are to reside on one or more servers whenthe sampling logic is executed, INQUIRY 1000. If so, then the one ormore servers to include the executables are identified, STEP 1002, andthe sampling logic for the one or more servers is transferred directlyto the servers' storage via, for instance, a File Transfer Protocol(FTP) or some other protocol or by copying through the use of a sharedfile system, STEP 1004. The logic is then installed on the servers, STEP1006.

Thereafter, or if there are no executables, a further determination ismade as to whether the sampling logic is to be deployed by having usersaccess the logic on a server or servers, INQUIRY 1008. If the users areto access the sampling logic on servers, then the server addresses thatare to store the logic are identified, STEP 1010. In one example, adetermination is made as to whether a proxy server is to be built tostore the sampling logic, INQUIRY 1012 (FIG. 10B). A proxy server is theserver that sits between a client application, such as a web browser,and a real server. It intercepts the requests to the real server to seeif it can fulfill the request itself. If not, it forwards the request tothe real server. Two primary benefits of the proxy server are to improveperformance and to filter requests. If a proxy server is to be built,then the proxy server is installed, STEP 1014.

Thereafter, or if a proxy server is not to be built, the sampling logicis sent to the server either via a protocol, such as file transferprotocol (FTP), or it is copied directly from the source files to theserver files via file sharing, STEP 1016. As another example, atransaction is sent to the one or more servers that includes thesampling logic and the servers process the transaction, then receive andcopy the logic to the servers' file systems.

After the sampling logic is stored at the servers, the users, via theirclient computers, access the logic on the servers and may copy at leasta portion of the logic to their client computers' file systems, STEP1018. The user then executes the program that installs the logic on theclient computer, STEP 1020. In a further example, the serversautomatically copy one or more aspects of the sampling logic to eachclient and then run the installation program for the logic at eachclient computer. This concludes one example of the deploymentprocessing, STEP 1022.

Returning to INQUIRY 1008 (FIG. 10A), if the logic is not to be deployedby having users access the logic on one or more servers, then processingcontinues with a determination as to whether the logic is to be deployedby sending the logic to users via e-mail, INQUIRY 1030. If so, the setof users where the logic is to be deployed is identified together withthe addresses of the user client computers, STEP 1032. The samplinglogic is sent via e-mail to each of the user's client computers, STEP1034 (FIG. 10B). The users receive the e-mail, STEP 1036, and detach thesampling logic from the e-mail to a directory on their client computers,STEP 1038. The user executes the program that installs the logic on theclient computer, STEP 1020, and exits the process, STEP 1022.

Returning to INQUIRY 1030 (FIG. 10A), if the sampling logic is not to bedeployed via e-mail, then a further determination is made as to whetherthe logic is to be sent directly to user directories on their clientcomputers, STEP 1040. If so, the user directories are identified, STEP1042. The sampling logic is directly transferred to the user's clientcomputer directory, STEP 1044 (FIG. 10B). This can be done in severalways, such as, but not limited to, sharing of the file systemdirectories and then copying from the sender's file system to therecipient user's file system, or alternatively, using a transferprotocol, such as file transfer protocol (FTP). The users access thedirectories on their client file systems in preparation for installingthe sampling logic, STEP 1046. The user executes the program thatinstalls the logic on the client computer, STEP 1020, and exits thedeployment process, STEP 1022.

Returning to INQUIRY 1040 (FIG. 10A), if the logic is not to be sentdirectly to the users' directories, then processing ends, STEP 1050.

Although an embodiment of deploying logic is provided, many variationscan be made without departing from the spirit of the present invention.

One or more aspects of the present invention can be provided, offered,deployed, managed, serviced, etc. by a service provider who offersmanagement of customer environments. For instance, the service providercan create, maintain, support, etc. computer code and/or a computerinfrastructure that performs one or more aspects of the presentinvention for one or more customers. In return, the service provider canreceive payment from the customer under a subscription and/or feeagreement, as examples. Additionally or alternatively, the serviceprovider can receive payment from the sale of advertising content to oneor more third parties.

In one aspect of the present invention, an application can be deployedfor performing one or more aspects of the present invention, asdescribed above. As one example, the deploying of an applicationcomprises providing computer infrastructure operable to perform one ormore aspects of the present invention.

As a further aspect of the present invention, a computing infrastructurecan be deployed comprising integrating computer readable code into acomputing system, in which the code in combination with the computingsystem is capable of performing one or more aspects of the presentinvention.

As yet a further aspect of the present invention, a process forintegrating computing infrastructure, comprising integrating computerreadable code into a computer system may be provided. The computersystem comprises a computer usable medium, in which the computer usablemedium comprises one or more aspects of the present invention. The codein combination with the computer system is capable of performing one ormore aspects of the present invention.

One or more aspects of the present invention can be included in anarticle of manufacture (e.g., one or more computer program products)having, for instance, computer usable media. The media has therein, forinstance, computer readable program code means or logic (e.g.,instructions, code, commands, etc.) to provide and facilitate thecapabilities of the present invention. The article of manufacture can beincluded as a part of a computer system or sold separately.

One example of an article of manufacture or a computer program productincorporating one or more aspects of the present invention is describedwith reference to FIG. 11. A computer program product 1100 includes, forinstance, one or more computer usable media 1102 to store computerreadable program code means or logic 1104 thereon to provide andfacilitate one or more aspects of the present invention. The medium canbe an electronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system (or apparatus or device) or a propagation medium.Examples of a computer readable medium include a semiconductor or solidstate memory, magnetic tape, a removable computer diskette, a randomaccess memory (RAM), a read-only memory (ROM), a rigid magnetic disk andan optical disk. Examples of optical disks include compact disk-readonly memory (CD-ROM), compact disk-read/write (CD-R/W) and DVD.

A sequence of program instructions or a logical assembly of one or moreinterrelated modules defined by one or more computer readable programcode means or logic direct the performance of one or more aspects of thepresent invention.

Advantageously, the measurement facility of one or more aspects of thepresent invention does not require an interrupt each time a sampling isperformed. Instead, an interrupt is performed only when it is determinedthat a marked sample data block is approximately full (e.g., not enoughspace to store next data entry) or at a desired time. By decreasing thenumber of interrupts, system performance is enhanced. Further, byfreeing the buffer, the same buffer is repeatedly used, therefore,decreasing the amount of buffer space needed.

One or more aspects of the present invention allow tradeoffs to be madeon how much storage is to be used to create the buffer versus theinterrupt frequency. The tradeoff can be based on the sampling intervalthat is used, the buffer size, the number of samples, and the number ofprocessors participating, as examples.

Although various embodiments are described above, these are onlyexamples. For instance, although various instructions are describedherein, one or more aspects of the present invention can use other thaninstructions, such as commands, functions, etc. Further, the format ofthe instructions may be different, including different fields, differentsize fields, different positioning, etc. Yet further, the information ofentities (e.g., request blocks, fields of entries, information blocks)described herein can have different information, the size of the fieldscan be different, as well as the positioning. Reserved fields or thosewith zeros may have been eliminated from the entities. Moreover, some ofthe information in the entities may not be used or needed for one ormore aspects of the present invention. Many other variations can bemade.

Although an example of a processing environment is provided herein, thisis only one example. Many other examples of processing environments mayincorporate and use one or more aspects of the present invention. Forexample, a processing environment may have only one CPU or anenvironment may be provided that is logically partitioned and one ormore of the logical partitions is executing a control program. In afurther example, a processing environment may be executing differentcontrol programs than described herein. Many other variations are alsopossible.

Further, other types of computing environments can benefit from one ormore aspects of the present invention. As an example, an environment mayinclude an emulator (e.g., software or other emulation mechanisms), inwhich a particular architecture (including, for instance, instructionexecution, architected functions, such as address translation, andarchitected facilities, such as architected registers) or a subsetthereof is emulated (e.g., on a native computer system having aprocessor and memory). In such an environment, one or more emulationfunctions of the emulator can implement one or more aspects of thepresent invention, even though a computer executing the emulator mayhave a different architecture than the capabilities being emulated. Asone example, in emulation mode, the specific instruction or operationbeing emulated is decoded, and an appropriate emulation function isbuilt to implement the individual instruction or operation.

In an emulation environment, a host computer includes, for instance, amemory to store instructions and data; an instruction fetch unit tofetch instructions from memory and to optionally, provide localbuffering for the fetched instruction; an instruction decode unit toreceive the instruction fetch unit and to determine the type ofinstructions that have been fetched; and an instruction execution unitto execute the instructions. Execution may include loading data into aregister for memory; storing data back to memory from a register; orperforming some type of arithmetic or logical operation, as determinedby the decode unit. In one example, each unit is implemented insoftware. For instance, the operations being performed by the units areimplemented as one or more subroutines within emulator software.

Further, a data processing system suitable for storing and/or executingprogram code is usable that includes at least one processor coupleddirectly or indirectly to memory elements through a system bus. Thememory elements include, for instance, local memory employed duringactual execution of the program code, bulk storage, and cache memorywhich provide temporary storage of at least some program code in orderto reduce the number of times code must be retrieved from bulk storageduring execution.

Input/Output or I/O devices (including, but not limited to, keyboards,displays, pointing devices, DASD, tape, CDs, DVDs, thumb drives andother memory media, etc.) can be coupled to the system either directlyor through intervening I/O controllers. Network adapters may also becoupled to the system to enable the data processing system to becomecoupled to other data processing systems or remote printers or storagedevices through intervening private or public networks. Modems, cablemodems, and Ethernet cards are just a few of the available types ofnetwork adapters.

The capabilities of one or more aspects of the present invention can beimplemented in software, firmware, hardware, or some combinationthereof. At least one program storage device readable by a machineembodying at least one program of instructions executable by the machineto perform the capabilities of the present invention can be provided.

The flow diagrams depicted herein are just examples. There may be manyvariations to these diagrams or the steps (or operations) describedtherein without departing from the spirit of the invention. Forinstance, the steps may be performed in a differing order, or steps maybe added, deleted, or modified. All of these variations are considered apart of the claimed invention.

As used herein, the term obtaining includes, but is not limited to,receiving, being provided, retrieving, determining, accessing, etc.

Although embodiments have been depicted and described in detail herein,it will be apparent to those skilled in the relevant art that variousmodifications, additions, substitutions and the like can be made withoutdeparting from the spirit of the invention and these are thereforeconsidered to be within the scope of the invention as defined in thefollowing claims.

What is claimed is:
 1. A computer program product for executing amachine instruction in a central processing unit, the computer programproduct comprising: a non-transitory computer readable storage mediumreadable by a processing circuit and storing instructions for executionby the processing circuit for performing a method comprising: obtaininga machine instruction for execution, the machine instruction beingdefined for computer execution according to a computer architecture, themachine instruction comprising: an opcode field identifying a setsampling controls instruction; and a first field identifying a generalregister, the contents of which are added to the contents of a secondfield to form a second operand address; and executing the machineinstruction, the executing comprising: activating sampling for one ormore sampling intervals to obtain information relating to processing ofthe central processing unit, wherein the activating sampling comprisesat least one of activating basic sampling to obtain a set of architectedsample data or activating diagnostic sampling to obtain a set ofnon-architected sample data; and placing in one or more controlregisters one or more sampling controls of a request block located inone or more storage locations designated by the second operand address.2. The computer program product of claim 1, wherein the set ofarchitected sample data comprises at least one of an instructionaddress, a primary address space number and state information relatingto the central processing unit.
 3. The computer program product of claim1, wherein the set of non-architected sample data comprises datarelating to hardware design.
 4. The computer program product of claim 1,wherein the activating sampling comprises activating basic sampling, andwherein the one or more control registers comprises informationregarding one or more instructions executed by the central processingunit.
 5. The computer program product of claim 1, wherein the requestblock comprises at least one of: a size indicator field specifying amaximum buffer size indicator; a host indicator, responsive to beingset, specifying a host; a basic sampling enable control, responsive tobeing set, specifying basic sampling; a diagnostic sampling enablecontrol, responsive to being set, specifying diagnostic sampling; abasic sampling activation control, responsive to being set, specifyingbasic sampling activation; a diagnostic sampling activation control,responsive to being set, specifying diagnostic sampling activation; asampling interval; contents of a table entry address register; andcontents of a data entry address register.
 6. The computer programproduct of claim 5, wherein one or more controls of the basic samplingenable control, the diagnostic sampling enable control, the basicsampling activation control or the diagnostic sampling activationcontrol are set responsive to a basic sampling function and a diagnosticsampling function making a valid state transition.
 7. The computerprogram product of claim 5, wherein the placing comprises placing themaximum buffer size indicator, the host indicator, the samplinginterval, the contents of the table entry address register and thecontents of the data entry address register in the one or more controlregisters, responsive to a sampling function being set to an activestate.
 8. The computer program product of claim 7, wherein the placingcomprises placing the maximum buffer size indicator, the host indicator,the sampling interval, the contents of the table entry address registerand the contents of the data entry address register in the one or morecontrol registers, responsive to a sampling function being set to anactive state and responsive to the sampling interval being within asupported range.
 9. The computer program product of claim 5, wherein theexecuting comprises setting a condition code, wherein the condition codeis set to 0 responsive to setting the basic sampling enable control, thediagnostic sampling enable control, the basic sampling activationcontrol and the diagnostic sampling activation control.
 10. The computerprogram product of claim 1, wherein the request block is 64 bytes andincludes: bit 0 specifying a maximum buffer size indicator; bit 1indicating a host, responsive to the central processing unit running ata logical partition level; bit 54 specifying a basic sampling enablecontrol; bit 55 specifying a diagnostic sampling enable control; bit 62specifying a basic sampling activation control; and bit 63 specifying adiagnostic sampling activation control.
 11. The computer program productof claim 10, wherein the request block further includes: a samplinginterval; contents of a table entry address register; and contents of adata entry address register.
 12. The computer program product of claim1, wherein the request block comprises contents of a table entry addressregister, the contents of the table entry address register indicating acurrent entry of a sample data block, the current entry of the sampledata block comprising at least one of a basic sampling data entry or adiagnostic sampling data entry.
 13. The computer program product ofclaim 12, wherein the request block comprises contents of a data entryaddress register, the contents of the data entry address registerindicating a next entry of the sample data block.
 14. The computerprogram product of claim 12, wherein the basic sampling data entrycomprises at least one of a number of unique instructions completedduring a sampling cycle, and an address of an instruction executedduring the sampling cycle.
 15. The computer program product of claim 14,wherein the basic sampling data entry comprises at least one of a dataentry format code, a data address translation mode, a wait stateindicator, a problem state indicator, an address space control, aninvalid indicator, and a primary address space number.
 16. The computerprogram product of claim 15, wherein the basic sampling data entrycomprises at least one of a host program parameter and a guest programparameter.
 17. The computer program product of claim 12, wherein thediagnostic sampling data entry comprises non-architected sample data.18. The computer program product of claim 17, wherein the diagnosticsampling data entry comprises at least one of a data entry format code,a maximum buffer size and an invalid indicator.
 19. A computer systemfor executing a machine instruction in a central processing unit, thecomputer system comprising: a memory; and a processor in communicationswith the memory, wherein the computer system is configured to perform amethod, said method comprising: obtaining a machine instruction forexecution, the machine instruction being defined for computer executionaccording to a computer architecture, the machine instructioncomprising: an opcode field identifying a set sampling controlsinstruction; and a first field identifying a general register, thecontents of which are added to the contents of a second field to form asecond operand address; and executing the machine instruction, theexecuting comprising: activating sampling for one or more samplingintervals to obtain information relating to processing of the centralprocessing unit, wherein the activating sampling comprises at least oneof activating basic sampling to obtain a set of architected sample dataor activating diagnostic sampling to obtain a set of non-architectedsample data; and placing in one or more control registers one or moresampling controls of a request block located in one or more storagelocations designated by the second operand address.
 20. The computersystem of claim 19, wherein the set of architected sample data comprisesat least one of an instruction address, a primary address space numberand state information relating to the central processing unit.
 21. Thecomputer system of claim 19, wherein the set of non-architected sampledata comprises data relating to hardware design.
 22. The computer systemof claim 19, wherein the request block comprises contents of a tableentry address register, the contents of the table entry address registerindicating a current entry of a sample data block, the current entry ofthe sample data block comprising at least one of a basic sampling dataentry or a diagnostic sampling data entry.
 23. The computer system ofclaim 22, wherein the request block comprises contents of a data entryaddress register, the contents of the data entry address registerindicating a next entry of the sample data block.
 24. A method ofexecuting a machine instruction in a central processing unit, the methodcomprising: obtaining a machine instruction for execution, the machineinstruction being defined for computer execution according to a computerarchitecture, the machine instruction comprising: an opcode fieldidentifying a set sampling controls instruction; and a first fieldidentifying a general register, the contents of which are added to thecontents of a second field to form a second operand address; andexecuting the machine instruction, the executing comprising: activatingsampling for one or more sampling intervals to obtain informationrelating to processing of the central processing unit, wherein theactivating sampling comprises at least one of activating basic samplingto obtain a set of architected sample data or activating diagnosticsampling to obtain a set of non-architected sample data; and placing inone or more control registers one or more sampling controls of a requestblock located in one or more storage locations designated by the secondoperand address.
 25. The method of claim 24, wherein the request blockcomprises contents of a table entry address register, the contents ofthe table entry address register indicating a current entry of a sampledata block, the current entry of the sample data block comprising atleast one of a basic sampling data entry or a diagnostic sampling dataentry.